From 0a7682998d60cf02caab772ba74955baf1ad806e Mon Sep 17 00:00:00 2001
From: "qingyi.liu" <qingyi.liu@17zuoye.com>
Date: Wed, 19 May 2021 11:22:07 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0142.=E7=8E=AF=E5=BD=A2?=
 =?UTF-8?q?=E9=93=BE=E8=A1=A8IIjavascript=E7=89=88=E6=9C=AC?=
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---
 problems/0142.环形链表II.md | 44 +++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/problems/0142.环形链表II.md b/problems/0142.环形链表II.md
index b3a53c07..71f5cc4c 100644
--- a/problems/0142.环形链表II.md
+++ b/problems/0142.环形链表II.md
@@ -258,6 +258,50 @@ Go：
 }
 ```
 
+javaScript
+
+```js
+// 两种循环实现方式
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+// 先判断是否是环形链表
+var detectCycle = function(head) {
+    if(!head || !head.next) return null;
+    let slow =head.next, fast = head.next.next;
+    while(fast && fast.next && fast!== slow) {
+        slow = slow.next;
+        fast = fast.next.next; 
+    }
+    if(!fast || !fast.next ) return null;
+    slow = head;
+    while (fast !== slow) {
+        slow = slow.next;
+        fast = fast.next;
+    }
+    return slow;
+};
+
+var detectCycle = function(head) {
+    if(!head || !head.next) return null;
+    let slow =head.next, fast = head.next.next;
+    while(fast && fast.next) {
+        slow = slow.next;
+        fast = fast.next.next;
+        if(fast == slow) {
+            slow = head;
+            while (fast !== slow) {
+                slow = slow.next;
+                fast = fast.next;
+            }
+            return slow;
+        }
+    }
+    return null;
+};
+```
+
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)